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Extraction of sediments with phosphoric acid (0.5M) and hydroxylamine hydrochloride (0.1M) allowed the measurement of labile arsenic species while preserving the two redox states of arsenic. The forms and concentrations of arsenic species were measured using HPLC–ICP-MS. A Hamilton PRP X-100 strong anion exchange column using a 20mM ammonium phosphate buffer (pH 6 and 9.2) was used to separate arsenic species. Recoveries of sediments spiked with As(V) were quantitative whereas for sediments spiked with As(III) recoveries of between 89 and 104% were obtained from four oxic certified reference sediments and an anoxic sediment. Application of the method to sediment samples from the marine Lake Macquarie, NSW, Australia, indicate that anoxic sediments can contain high concentrations of As(III), and two arsenosugars (sulfonate-ribose and sulfate-ribose). Extraction efficiencies for arsenic …